History of the National Hockey League/1917–1942/Rules and innovations

Clint Benedict, shown in 1923, became the first goaltender to wear facial protection in a game in 1930.

The 1920s saw numerous rule innovations as the sport evolved. The Ottawa Senators won three Stanley Cups in the early 1920s using strong defence, and the goaltending of Clint Benedict, who recorded a record five shutouts in a 24-game season in 1921. The Senators employed a strategy where they kept both defencemen and a forward in their own zone at all times after they gained a lead. After the Senators' third championship in 1924, Frank Calder made it illegal for more than two players to be in their defensive zone if the puck was not.

Defence continued to dominate the game, however, as in 1928–29, the league averaged less than three goals per game. Canadiens goaltender George Hainsworth set what remains a league record with 22 shutouts in only 44 games. As a result, the league allowed the use of the forward pass in all zones beginning in 1929. Previously, forward passing was allowed only in the defensive and neutral zones. The change saw offence rise to 6.9 goals per game over the first third of the season as players began to park themselves on their opponent's goal crease. The league responded by introducing the offside rule early in the 1929–30 season, barring offensive players from entering their opponent's zone before the puck. Despite this, Cooney Weiland, Dit Clapper and Howie Morenz all broke the 40-goal mark, the first players to do so since Joe Malone scored 44 in the NHL's first season.

Boston Bruins governor, Charles Adams had long disliked the defensive tactic of shooting the puck the length of the ice ("icing") to relieve pressure. After the New York Americans iced the puck 61 times in a 3–2 win in Boston during the 1936–37 season, Adams promised that he would see to it that the Bruins played a similar style in New York. True to his word, the Bruins iced the puck 87 times in a 0–0 tie at Madison Square Garden. The NHL introduced the icing rule the following season, calling for a faceoff in the offending team's defensive zone after each infraction.

Art Ross was an early innovator of the game. He designed rounded goal nets that became the league standard, replacing the old square-backed nets. He also successfully argued for using synthetic rubber pucks rather than real rubber. Some of Ross' inventions did not catch on, however. Ross invented a puck with rounded edges that was rejected after goaltenders complained about the erratic behaviour of the pucks. He also created a two-piece hockey stick that had a metal shaft and replaceable wooden blades. The idea did not catch on at the time, but became a forerunner to modern composite sticks used today.